ES2977968T3 - Electrical switching apparatus and sealing gasket assembly therefor - Google Patents

Abstract

A movable contact assembly (50) is provided for an electrical switching apparatus (10). The movable contact assembly (50) includes a plurality of shunts (54) and a carriage assembly (52) that includes two side walls (70, 74) and a contact arm assembly (65). The side walls of the carriage assembly (70, 74) are arranged in a spaced apart relationship. The contact arm assembly (65) includes a plurality of contact arms (58A, 58B, 58C, 58D), a plurality of insulating elements (56A, 56B), a plurality of movable contacts (60), and a shaft (62). Each contact arm (58) defines an opening. A movable contact (50) is disposed on each contact arm (58). Each contact arm (58) is rotatably coupled to the shaft (62) with the shaft (62) extending through the opening of the contact arm (58). Each isolation element (56A, 56B) is disposed adjacent to at least one contact arm (58). Each isolation element (56A, 56B) is coupled to, and in electrical communication with, the adjacent contact arm (58A, 58B, 58C, 58D). The shunts (54) are coupled to, and in electrical communication with, the isolation elements (56A, 56B). In this configuration, no shunt (54) is operatively coupled to a contact arm (65). (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Electrical switching apparatus and sealing gasket assembly therefor

Background

Field

The described concept generally relates to an electrical switching apparatus and, more particularly, to an electrical switching apparatus such as a circuit breaker. The described concept also relates to sealing gasket assemblies for circuit breakers.

Background information

Electrical switching devices, such as circuit breakers, provide protection to electrical systems against electrical fault conditions such as, for example, current overloads, short circuits, abnormal voltages, and other fault conditions. Typically, circuit breakers include an operating mechanism that opens electrical contact assemblies to interrupt the flow of current through the conductors of an electrical system in response to such fault conditions. The operating mechanism is designed to rapidly open and close separable contacts. The operating mechanism is structured to latch and thereby hold the contacts in a closed configuration. A trip unit is structured to detect overcurrent conditions. When an overcurrent condition is detected, the trip unit releases the latch of the operating mechanism, allowing biasing elements to bias the operating mechanism and contacts to an open configuration. A circuit breaker is generally assigned a size and a “resistance” value. The size of the circuit breaker is substantially related to the size of the circuit breaker housing assembly or frame. The resistance value of the circuit breaker involves a balance between the discharge forces generated by the electric currents flowing in the circuit breaker and the contact forces generated in the moving conductor by the operating mechanism.

Many low voltage circuit breakers employ a molded housing having two parts, a first half or front portion (e.g., a molded cover) and a second half or back portion (e.g., a molded base). The operating mechanism of such circuit breakers is frequently mounted on the front of the housing and typically includes an operating handle and/or button(s) that is(are) accessible at one end from outside the molded housing and is(are) coupled at the other end to a rotatable pole shaft. Electrical contact assemblies, which are also disposed within the molded housing, generally comprise a conductor assembly that includes a movable contact assembly having a plurality of movable contacts, and a stationary contact assembly having a plurality of corresponding stationary contacts. The movable contact assembly is electrically connected to a generally rigid conductor of the conductor assembly by flexible conductors, commonly referred to as shunts. The movable contact assembly includes a plurality of movable contact arms or fingers, each of which carries one of the movable contacts and is pivotally coupled to a contact arm support. The contact arm support is pivoted by a protrusion or arm on the polar axis of the circuit breaker operating mechanism to move the movable contacts between a first open position (not shown), wherein the movable contacts are not engaged or brought into electrical communication with the corresponding stationary contacts, and a second closed position (contact arm 58D, described below, is shown in the second position of Figure 1), wherein the movable contacts are engaged and brought into electrical communication with the corresponding stationary contacts. The contact arm support includes a contact spring assembly structured to bias the fingers of the movable contact assembly against the stationary contacts of the stationary contact assembly to provide and maintain contact pressure when the circuit breaker is closed and to accommodate wear.

The shunts typically comprise copper wires or layered copper strips, and are solidified at their ends by heat and pressure and then soldered to the rigid conductor at one end and to the contact arms of the moving contact assembly at the opposite end. One of the disadvantages associated with known metal wire or stranded type shunts is that they do not fit well within the limited space that is available between adjacent contact arms of the moving contact assembly. Specifically, the body of such shunts tends to expand outward and occupy a width greater than that of the finger, thus interfering with adjacent structures. The metal wires also tend to bunch up during short circuit events, which inhibits the flexibility of the assembly. This is problematic in view of the compound motion that the fingers experience as a result of the well-known “heel and toe” and/or “blow” arcing schemes commonly employed in low voltage circuit breakers. See, e.g., U.S. Patent No. 6,005,206.

To accommodate the motion of the contact finger during separation of a stationary contact, an elongated shunt is typically arranged in an “S” shape for use, i.e., in a “use shape”. That is, as used herein, a “use shape” is the general shape of the shunt, as opposed to, for example, the cross-sectional shape of a shunt prior to an overcurrent event. This may also be identified as a “rest shape”. In an electrical switching apparatus having a higher resistance value, e.g., a circuit breaker structured for a higher voltage, the elongated shunts create magnetic fields during an overcurrent event. These magnetic fields from adjacent shunts, as well as motion caused by the operating mechanism, cause the shunt to rapidly change shape into an extreme compound deflection, or colloquially, an extreme “ripple”, during an overcurrent event. This movement causes the shunt to wear and creates uncontrollable forces affecting the support and contact arms.

Layered strip-type shunts also present a number of unique disadvantages. Among them is the fact that they are typically V-shaped, so they have a single, relatively sharp bend that undesirably creates an area of stress concentration. This V-shape also consumes a substantial amount of valuable space within the molded housing of the circuit breaker.

Therefore, there is a problem with the size and configuration, including the manner of use, of the shunts. That is, the shunt loads are not isolated from the contact arms of the moving contact assembly, and longer shunts are subjected to extreme compound deflection.

Furthermore, when a current passes through the shunts, the shunts have a magnetic field that produces forces that act on other elements of the electrical contact assemblies. These magnetic fields and the corresponding forces are variable due to the variable configuration of the shunts, i.e. when the wires also tend to bunch together during short-circuit events. This is a disadvantage, as the variable forces either enhance or weaken the opening forces created by the operating mechanism. That is, having an operating mechanism that has variable opening characteristics is a disadvantage.

A related improvement to electrical contact assemblies is the use of a seal assembly. A seal assembly eliminates shunts by including a slotted conductor having a bifurcated member, such as a yoke, that supports a shaft member. The contact arm of the movable contact assembly is rotatably disposed on the shaft. The yoke laterally deflects against the contact arm of the movable contact assembly, i.e., the yoke firmly holds the contact arm of the movable contact assembly or “clamps” the contact arm of the movable contact assembly. The lateral deflection creates a torque on the contact arm of the movable contact assembly that resists rotation. The slotted conductor engages the conductor assembly. Thus, electricity flows through the conductor assembly, the slotted conductor, and the contact arm of the movable contact assembly before reaching the movable contact. See, e.g., U.S. Patent No. 4,245,203. In this configuration, the rotation of the contact arm is influenced, in part, by the lateral pressure or torque applied to the contact arm by the slotted conductor. It should be noted that, in this configuration, the lateral deflection torque is created by friction. Since friction is affected by the contact surface area on the yoke and contact arms of the moving contact assembly, manufacturing tolerances and other factors affect the torque. That is, the level of torque balance control could be improved.

In this configuration, the moving contact assembly is limited to a maximum of two contact arms. That is, the lateral deflection applied by the yoke must apply a deflection in a controlled manner to the contact arms of the moving contact assembly to control the stroke opening characteristics of each arm. This is only possible with a two-arm configuration because the torque applied by a yoke to a middle contact arm, that is, a contact arm between two other contact arms, cannot be controlled. That is, because the fingers typically have the same geometry, that is, the same shape, and rotate about the same axis, the contact area between adjacent surface of each finger can be large or small. That is, the “contact area” is variable due to the roughness/smoothness of each surface, resulting in a different number of contact points on each surface, deformation of the contact fingers, and other factors affecting the total area in actual contact on the lateral surface of each contact finger. This varying contact surface creates a difference in the coefficient of friction of the surfaces and variations in the coefficient of friction over the lateral surface of a single contact finger. Therefore, when the contact fingers are compressed laterally, each finger is subject to a varying torque due to the differences in friction. In a two-finger configuration, each finger is subject to the friction created by the yoke, which due to the smaller contact area is negligible relative to the larger lateral surface contact area and the lateral surface contact area. When there are two contact fingers, the friction acting on the lateral surface contact area is the same because it is the same lateral surface contact area. That is, by definition, the lateral surface contact area of a first contact arm disposed against a second contact arm is the same as the lateral surface contact area of that second contact arm disposed against that first contact arm.

This is not true for a stack of three or more contact arms. As an analogy, imagine an assembly of three or more paper plates in a stack with a central axis through the stack. Depending on how they are assembled, the flatness or lack of flatness creates more or less friction between adjacent plates. If an equal rotational force were applied to each plate, the plates would rotate at different rates due to the differences in friction between adjacent plates. This also applies to contact arms.

This is a disadvantage because the rating, i.e. the resistance value or size of the circuit breaker, is limited by the size of the contact arms of the moving contact assembly. That is, for a higher rating, the size of the contact arms of the moving contact assembly and therefore the size of the circuit breaker must be increased.

Therefore, there is a problem with the size and configuration of the sealing joint assemblies. As stated above, the level of torque balance control could be improved while still accommodating manufacturing tolerances. In addition, the limited number of contact arms of the moving contact assembly that current sealing joint assemblies allow is a problem.

An electrical switching apparatus with a higher resistance value may include elements of both a moving contact assembly and a closing joint assembly. That is, an air circuit breaker is structured to withstand higher currents and thus allow downstream circuit breakers to open during a relatively less intense overcurrent event. Thus, as an example, power may be cut off to a single room in a hospital, but not to the entire wing of the hospital. During a relatively more intense overcurrent event, the air circuit breaker will open. Furthermore, during such an overcurrent event, it is best for the air circuit breaker to open as quickly as possible. This is accomplished by having several fingers on a closing joint assembly of the air circuit breaker “snap open,” i.e., rotate rapidly, in response to a magnetic field generated by the overcurrent condition. In addition, in response to a trip unit sensing the same overcurrent condition, the air circuit breaker operating mechanism will actuate and pull the entire air circuit breaker closing joint assembly away from the stationary contacts. Therefore, the contact arms of the moving contact assembly are first “snapped open” and then the entire closing joint assembly is pulled away from the stationary contacts. Because the closing joint assembly is not attached to the conductor, the moving contact assembly included shunts to engage and provide electrical communication between the conductor and the closing joint assembly. In view of the higher voltage for which an air circuit breaker is rated, the amount of “ripple” experienced by a shunt during an overcurrent condition is increased. That is, an air circuit breaker utilizing a moving closing joint assembly is subject to the problems of both closing joint assemblies and shunts noted above.

Therefore, there is a need for moving contact assembly elements (e.g. shunts) that solve the problems indicated above. There is a further need for moving contact assembly elements (e.g. a sealing gasket assembly) that solve the problems indicated above. Consequently, there is scope for improvement of conductor assemblies for electrical switching devices such as, for example, air circuit breakers.

Furthermore, reference is made to US-2008 088 394 A1, relating to a contact spring assembly for an electrical switching apparatus including a movable contact assembly and a fixed contact assembly having fixed electrical contacts. The movable contact assembly includes a support assembly and movable contact arms pivotally coupled to the support assembly and carrying movable electrical contacts. The contact spring assembly includes a first contact spring housing member, a second contact spring housing member coupled to and disposed opposite the first contact spring housing member, a spring guide disposed between and coupled to at least one of the first and second contact spring housing members and includes spring holes, springs received in the spring holes and sliders coupled to the springs. The springs and sliders individually bias the movable contact arms and the movable electrical contacts into engagement with the corresponding fixed electrical contacts.

Summary

The concept described and claimed addresses the problems and needs noted above by providing a movable contact assembly for an electrical switching apparatus as set forth in claim 1. Other embodiments are described, inter alia, in the dependent claims. The movable contact assembly includes a plurality of shunts and a carriage assembly including two side walls and a contact arm assembly. The side walls of the carriage assembly are arranged in a spaced apart relationship. The contact arm assembly includes a plurality of contact arms, a plurality of insulating members, a plurality of movable contacts, and a shaft. Each contact arm defines an opening. A movable contact is disposed on each contact arm. Each contact arm is rotatably coupled to the shaft, the shaft extending through the opening of the contact arm. Each insulating member is disposed adjacent to at least one contact arm. Each insulating member is coupled to and brought into electrical communication with the adjacent contact arm. The shunts are coupled to, and brought into electrical communication with, the insulating members. In this configuration, the area of each contact arm that frictionally engages another element is limited to the isolation member. This friction force generated by the smaller contact area can be more easily controlled. Also, in this configuration, no shunt is operatively engaged to a contact arm.

Brief description of the drawings

The described concept can be fully understood from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:

Figure 1 is a partially exploded sectional view of a circuit breaker, according to a non-limiting embodiment of the described concept, showing the cover in a simplified form;

Figure 2 is an enlarged view of a portion of a movable contact assembly;

Figure 3 is an isometric view of the moving contact assembly;

Figure 4 is an exploded isometric view of the movable contact assembly of Figure 3;

Figure 5 is a side elevation view of the movable contact assembly of Figure 4;

Figure 6 is a sectional view taken along line 6-6 of Figure 5;

Figure 7 is a sectional view taken along line 7-7 of Figure 5;

Figure 8 is an isometric view of a contact arm assembly;

Figure 9A is a sectional view of a contact arm assembly according to one embodiment; Figure 9B is a sectional view of a contact arm assembly according to another embodiment; Figure 9C is a sectional view of a contact arm assembly according to another embodiment not covered by the present invention;

Figures 10A, 10B, 10C and 10D are isometric views, top plan, side elevation and bottom plan, respectively, of a first isolation member; and

Figures 11A, 11B, 11C, and 11D are isometric views, top plan, side elevation, and bottom plan, respectively, of a second isolation member.

Description of the preferred embodiments

Directional expressions used herein, such as, for example, clockwise, counterclockwise, left, right, top, bottom, up, down, and derivatives thereof, refer to the orientation of the elements shown in the drawings and are not limiting of the claims unless expressly specified herein.

As used herein, the singular forms of “a”, “an” and “the” include references to the plural unless the context clearly dictates otherwise.

As used herein, the word “unitary” means that a component is created as a single piece or unit. That is, a component that includes pieces that are created separately and then coupled together as a unit is not a “unitary” component or body. Furthermore, as used herein, portions or elements of a “unitary” body are “coupled” together.

As used herein, a “coupling assembly” includes two or more couplings or coupling components. The components of a coupling or coupling assembly are generally not part of the same element or another component. As such, the components of a “coupling assembly” may not be described at the same time in the following description.

As used herein, a “coupling” or “coupling component(s)” is one or more components of a coupling assembly. That is, a coupling assembly includes at least two components that are structured to mate with each other. The components of a coupling assembly are understood to be compatible with each other. For example, in a coupling assembly, if one coupling component is a snap-in receptacle, the other coupling component is a snap-in projection, or if one coupling component is a bolt, the other coupling component is a nut. It is further understood that an opening or passage through which another coupling component extends is also a coupling component.

As used herein, the statement that two or more parts or components are “coupled” means that the parts are joined or function together, either directly or indirectly, i.e., through one or more intermediate parts or components, so long as a connection occurs. As used herein, “directly coupled” means that two elements are directly in contact with each other. As used herein, “fixedly coupled” or “fixed” means that two components are coupled to move as a unit while maintaining a constant orientation relative to each other. Thus, when two elements are coupled, all parts of those elements are coupled. However, a description of a specific portion of a first element coupled to a second element, e.g., a first axle end coupled to a first wheel, means that the specific portion of the first element is disposed closer to the second element with respect to the other portions thereof. Furthermore, a first object resting on a second object, which is held in place solely by gravity, is not “coupled” to the second object unless the first object is otherwise connected to the second object. That is, for example, a book on a table is not coupled to the table, but a book attached to a table is coupled to the table.

As used herein, “temporarily coupled” means that two components are coupled in a manner that allows the components to be easily disengaged without damaging the components. For example, elements that are coupled by a nut/bolt coupling are “temporarily coupled,” while elements that are welded together are not.

As used herein, the statement that two or more parts or components “engage” with each other means that the elements exert a force or bias against each other, either directly or through one or more intermediate elements or components.

As used herein, “operatively engaged” means “engaged and moved.” That is, when “operatively engaged” is used in connection with a first component that is structured to move a second movable or rotatable component, it means that the first component applies a force sufficient to cause the second component to move. For example, a screwdriver may contact a screw. When no force is applied to the screwdriver, the screwdriver is simply “engaged” to the screw. If an axial force is applied to the screwdriver, the screwdriver is pressed against the screw and “engages” with the screw; however, when a rotational force is applied to the screwdriver, the screwdriver “operatively engages” with the screw and causes the screw to rotate. As used herein, “operatively engaged” means “engaged and held in a selected position.” That is, a compressed spring held in place by a latch is “operatively engaged” by the latch because the latch holds the spring in a compressed state.

As used herein, the term “several” means one or an integer greater than one (i.e., a plurality).

As used herein, “associated” means that the elements are part of the same assembly and/or that they function together or act on one another or on each other in some way. For example, an automobile has four tires and four hubcaps. Even though all of the elements are coupled together as part of the automobile, each hubcap is understood to be “associated” with a specific tire.

As used herein, “match” indicates that two structural components are sized and shaped to be similar to each other and can mate with a minimum amount of friction. Thus, an opening that “matches” a member is sized to be slightly larger than the member so that the member can pass through the opening with a minimum amount of friction. This definition is modified if the two components are to fit “snugly” together or “match without play.” In that situation, the difference in the size of the components is even smaller, so the amount of friction is increased. If the member defining the opening and/or the component inserted into the opening is made of a deformable or compressible material, the opening may be even slightly smaller than the component being inserted into the opening. This definition is further modified if the two components are to “substantially match.” “Substantially match” means that the size of the opening is very close to the size of the member inserted into the opening; that is, not so close as to cause substantial friction, as with a snug fit, but with more contact and friction than a “matching fit,” i.e., a “slightly larger” fit. Also, with respect to a surface formed by two or more elements, a “matching” shape means that the surface characteristics, e.g., curvature, are similar.

As used herein, “structured to [verb] or ‘be an [X]’” means that the identified element or assembly has a structure that is shaped, sized, arranged, coupled, and/or configured to perform the identified verb or to be that which is identified in the infinitive phrase. For example, a member that is “structured to move” is movably coupled to another member and includes elements that cause the member to move or the member is otherwise configured to move in response to other elements or assemblies. As such, as used herein, “structured to [verb] or ‘be an [X]’” indicates a structure and not a function. Furthermore, as used herein, “structured to [verb] or ‘be an [X]’” means that the identified element or assembly is intended to, and is designed to, perform the identified verb or be an [X]. Thus, an element that is only possibly “capable” of performing the identified verb, but is not intended to, and is not designed to, perform the identified verb is not “structured to [verb] or ‘be an [X]’”.

As used herein, a “path” or “travel path” is the space through which an element moves when in motion.

As used herein, and with reference to a seal assembly, “floating” or “floatingly engaging” means that the elements that are rotatably engaged to an axle are not subject to any lateral compression and/or engagement by the sidewall of a carriage, that the elements that are rotatably engaged to an axle are capable of longitudinal displacement about the axle, and that any friction created by the compression forces generates “substantially equivalent friction.” That is, each contact arm rotatably disposed on the same axle is exposed to substantially the same frictional forces. It is understood that the frictional forces to which a contact arm is exposed are substantially created by engagement (i.e., biasing) on the lateral sides of the contact arm. It is understood that those skilled in the art understand how to control the friction on the lateral sides of the contact arm. As an example, a first contact arm may have relatively small lateral contact surfaces with a relatively higher coefficient of friction with adjacent elements, while a second contact arm may have relatively large lateral contact surfaces with a relatively lower coefficient of friction; if the friction generated at the first and second contact arms is generally equivalent, then the first and second contact arms are subject to “substantially equivalent friction” and “float” on the axis.

As used herein, “reduced friction” is the friction created by an element engaging and rotating against a “reduced engagement area.” As used herein, “reduced engagement area” means an area between about 1% and 85% of the surface area of one of the side surfaces 166, 168 of the contact arm body. As used herein, “very reduced friction” is the friction created by an element engaging and rotating against a “very reduced engagement area.” As used herein, “very reduced engagement area” means an area between about 1% and 50% of the total surface area of the side surfaces 166, 168 of the contact arm body. As used herein, “extremely low friction” is the friction created by an element engaging and rotating against an “extremely low engagement area.” As used herein, “extremely low engagement area” means an area between about 1% and 15% of the total surface area of the side surfaces 166, 168 of the contact arm body.

As used herein, and with reference to a seal assembly, “freely” when used to modify “float” or “floatingly coupled” means, in addition to “float” as defined above, that the elements rotatably disposed on an axis are not subject to any substantial frictional force about the axis. Stated alternatively, when an element defines an opening that corresponds to the axis, or is larger than the axis, the minimum friction is not substantial and the element “floats freely” on the axis.

As used herein, and with reference to a seal assembly, “fully” when used to modify “floating” or “floatingly coupled” means that the rotatable elements coupled to a shaft are longitudinally movable along substantially the entire length of the shaft. That is, each element is not movable along substantially the entire length of the shaft, but collectively, the elements are not constrained from moving along substantially the entire length of the shaft by a construction such as, but not limited to, a flange disposed at the mid-portion of the shaft.

As used herein, and with reference to a seal assembly, “partially” when used to modify “floating” or “floatingly coupled” means that the rotatable elements coupled to a shaft may not move longitudinally along substantially the entire length of the shaft. That is, the elements are constrained to move substantially along the entire length of the shaft by a construction such as, but not limited to, a flange disposed at the mid-portion of the shaft. Elements disposed to one side of, or between, the limiting construction(s) may move on the portion of the shaft to that side of, or between, the limiting construction(s). As before, this does not mean that each element disposed on one side of, or between, the limiting construction(s) can move on the portion of the axis on that side of, or between, the limiting construction(s), but rather, collectively, the group of elements disposed on one side of, or between, the limiting construction(s) can move on the portion of the axis on that side of, or between, the limiting construction(s).

Figures 1 and 2 show an electrical switching apparatus 10, which in one illustrative embodiment is an air circuit breaker 11, which includes a housing assembly 12, a conductor assembly 20, a trip unit 22 (shown schematically), and an operating mechanism 24 (Figure 5, shown schematically). The housing assembly 12 includes a first half or front portion 14 (e.g., a molded cover) and a second half or rear portion 16 (e.g., a molded base) that, when joined, define a substantially enclosed space 18. The conductor assembly 20, trip unit 22, and operating mechanism 24 are disposed substantially in the enclosed space 18 of the housing assembly.

The conductor assembly 20 includes several pole assemblies 30 (one shown). That is, there is a similar set of conductive elements for each pole of the air circuit breaker 11. Since the pole assemblies 30 are similar, only one will be described. Each pole assembly 30 includes a line conductor 32 (shown schematically), a contact assembly 40, and a load conductor 34 (shown schematically). Each of the line conductor 32 and the load conductor 34 includes an external terminal (not shown) structured to engage a line or load, respectively.

Each contact assembly 40 includes a stationary contact 42 and a movable contact assembly 50. The stationary contact 42, in an illustrative embodiment, engages, is directly coupled to, or is secured to the line conductor 32. The movable contact assembly 50 includes a plurality of movable contacts 60, described below, that are structured to move between a first open position, wherein the movable contacts 60 do not engage the stationary contact 42 and are not brought into electrical communication therewith, and a second closed position, wherein the movable contacts 60 engage the stationary contact 42 and are brought into electrical communication therewith. It is understood that the operating mechanism 24 is structured to move the movable contacts 60 between the two positions, either manually or to move the movable contacts 60 from the second position to the first position in response to an actuation by the trip unit. In addition, the movable contacts 60 are structured to “snap open” in response to an overcurrent condition, as described below.

In an illustrative embodiment, each movable contact assembly 50 includes a carriage assembly 52, a plurality of shunts 54, a plurality of isolation members 56, a plurality of contact arms 58, a plurality of movable contacts 60, a shaft assembly 62, and a biasing assembly 64. Furthermore, as used herein, the combination of the number of shunts 54, the number of isolation members 56, the number of contact arms 58, the number of movable contacts 60, and the shaft assembly 62 will be identified as the contact arm assembly 65 (Figure 8). Furthermore, the elements that are rotatably coupled to the shaft assembly 62 are collectively identified hereinafter as the “rotating elements” 66. That is, as used herein, the “rotating elements” 66 include the isolation elements 56 and the contact arms 58, as well as any medial spacers 63, described below as part of the shaft assembly 62.

In an illustrative embodiment, the carriage assembly 52 is fabricated from steel, while the number of leads 54, the number of insulation members 56, the number of contact arms 58, and the number of movable contacts 60 are fabricated from copper or another metal more conductive than steel.

In general, and as described in detail below, the rotating elements 66 are floatably, or freely and floatably, coupled to the axle assembly 62. Thus, the contact arm assembly 65 is floatably, or freely and floatably, coupled to the carriage assembly 52. That is, the contact arms 58 generate “substantially equivalent friction” during rotation. Furthermore, in an illustrative embodiment, the contact arms 58 are compressed to the axle assembly 62 by a compression device 67. In an illustrative embodiment, the compression device 67 is a series of Belleville washers 204, which are explained below. The elements that are engaged by and include the contact arms 58 by the compression device 67 each have a reduced engagement area, a very reduced engagement area, or an extremely reduced engagement area. In this configuration, the friction forces are controllable, which solves the problems indicated above.

In an illustrative embodiment, as shown in Figures 3 and 4, the carriage assembly 52 includes two side walls; a first side wall 70 and a second side wall 74, and a plurality of spacers 76. Each side wall 70, 74 of the carriage assembly includes an interior side surface 71, 73, respectively. The spacers 76 are structured to, and do, maintain the side walls 70, 74 of the carriage assembly in a spaced apart relationship. In an illustrative embodiment, the side walls 70, 74 of the carriage assembly define a pivot point 78 and an operating mechanism engagement 80. The pivot point 78 of the carriage assembly includes, in an illustrative embodiment, a circular lug 82 extending from each side wall 70, 74 of the carriage assembly. The pivot point lug 82 of each carriage assembly is structured to rotatably engage the housing assembly 12. The carriage assembly operating mechanism coupling 80 is spaced apart, in an illustrative embodiment, from the carriage assembly pivot point 78. In this configuration, when the operating mechanism 24 is actuated, the carriage assembly 52 rotates about the carriage assembly pivot point 78. Each of the carriage assembly side walls 70, 74 further defines a series of mounting openings 85 for the spacers 76 and the diverter assembly 64.

Each of the carriage assembly side walls 70, 74 further defines an axle opening 84. Each axle opening 84 is generally circular. When the carriage assembly side walls 70, 74 are assembled and arranged in a spaced apart relationship, the axle openings 84 align. There are at least three variations of the axle assembly 62 that engages the carriage assembly side walls 70, 74. That is, the axle assembly 62 engages the carriage assembly side walls 70, 74 at the aligned axle openings 84, but, in one embodiment, the biasing assembly 64 of the axle assembly 62, explained below, is disposed within the axle openings 84. In another embodiment, the biasing assembly 64 of the axle assembly 62 is disposed within and against the carriage assembly side walls 70, 74. In both configurations, the axle assembly 62 is rotatably coupled to the side walls 70, 74 of the carriage assembly. In another illustrative embodiment, the axle assembly 62 is secured to the side walls 70, 74 of the carriage assembly. That is, for example, the axle assembly 62 may include a non-circular portion and the axle openings 84 may have a corresponding non-circular shape.

In an illustrative embodiment, each side wall 70, 74 of the carriage assembly includes an anti-rotation lug opening 86. An anti-rotation lug opening 86 is sized and shaped to correspond to an anti-rotation lug 140 on an isolation member 56. Each anti-rotation lug opening 86 has a shape that is not generally circular. As shown, each anti-rotation lug opening 86 is square.

As shown in Figures 1 and 8, each shunt 54 includes an elongated body 90. In an illustrative embodiment, each shunt body 90 has a length of approximately 1.5 inches (3.81 cm), which as used herein is a “reduced length.” That is, relative to the shunts described above, the shunts 54 described herein have a “reduced length.” In addition, each shunt 54 is arranged in a “minimally curved configuration.” As used herein, “in a minimally curved configuration” means a curvature of an arc with an inner radius greater than about 40 inches (1016 cm).

It should be noted that a generally straight line is, as used herein, an arc with an infinite radius and is included within the definition of a “minimally curved configuration.” A shunt 54 with a reduced length and that is arranged in a minimally curved configuration is only subjected to a minimal amount of deflection or “waviness” during an overcurrent event. Therefore, a shunt 54 with a reduced length and that is arranged in a minimally curved configuration solves the problems set forth above. In an illustrative embodiment, each shunt 54 also includes a rotatable coupling element 57 which, in an illustrative embodiment, is a generally cylindrical lug 59, shown schematically.

Each isolation member 56 is structured to allow each contact arm 58 to float about the axis 210, described below, and to isolate the contact arms 58 from the forces generated by the shunts 54. That is, as used herein and with reference to the isolation members 56, “isolate” or “isolation” means separating the bias created by the shunts 54 during an overcurrent condition from the contact arms 58 and does not refer to electrical isolation or interruption of the current between the shunt 54 and the contact arms 58. In an illustrative embodiment, where there are four contact arms 58, as described below, there are two isolation members 56. The isolation members 56 are substantially similar, so only one will be described.

As shown in Figures 10A-10C and 11A-11C, each isolation member 56 includes a body 100 having a front surface 102, a rear surface 104, a first side surface 106, and a second side surface 108. In an illustrative embodiment, the isolation member body 100 has a thickness, i.e., the distance between the first side surface 106 of the isolation member body and the second side surface 108 of the isolation member body, that is more than about three times the thickness of a contact arm body 160, described below. The isolation member body 100 also includes a contact arm tab 110 extending from the front surface 102 of the isolation member body. The contact arm tab 110 includes two side surfaces; a first side surface 112 and a second side surface 114. A contact arm tab opening 116 extends between the first side surface 112 of the contact arm tab and the second side surface 114 of the contact arm tab. The contact arm tab opening 116 is generally circular and corresponds to the axis 210, which is described below.

In an illustrative embodiment, the contact arm tab 110 has a thickness, i.e., the distance between the first side surface 112 of the contact arm tab and the second side surface 114 of the contact arm tab, that is approximately the same thickness as that of the contact arm body 160, described below. As described below, each of the side surfaces 112, 114 of the contact arm tab engages the side surfaces 166, 168 of the contact arm body, described below. To allow each contact arm to “float,” it is desirable to limit contact between the side surfaces 166, 168 of the contact arm body and the side surfaces 112, 114 of the contact arm tab. Accordingly, in an illustrative embodiment, each contact arm tab side surface 112, 114 has a “reduced engagement area,” a “very reduced engagement area,” or an “extremely reduced engagement area.” With a “reduced engagement area,” a “very reduced engagement area,” or an “extremely reduced engagement area,” the area of the contact arm body side surfaces 166, 168 subjected to friction, as described below, is reduced (either greatly reduced or extremely reduced), thereby having a reduced and more controllable effect on the torque created when the contact arms 58 rotate. Therefore, the “reduced engagement area,” the “very reduced engagement area,” or the “extremely reduced area” of the contact arm tab side surfaces 112, 114 solves the problems noted above.

In this configuration, the front surface 102 of the isolation member body is divided into a right side 120, a contact arm tab 110 (described above), and a left side 122. The right side 120 and the left side 122 of the front surface of the isolation member body are each a generally arcuate surface 126 with a radial lug 128. That is, the radial lug 128 is a lug that extends generally toward the center of the arc defined by the front surface 102 of the isolation member body on the right side 120 and the left side 122.

Furthermore, in an illustrative embodiment, and as noted above, the distance between the first side surface 106 of the isolation member body and the second side surface 108 of the isolation member body is more than about three times the thickness of a contact arm body 160. Furthermore, the thickness of the contact arm tab 110 is approximately the same as the thickness of a contact arm body 160, which is described below. In this configuration, and when a contact arm body 160 is disposed on either side of the contact arm tab 110, the total thickness of the stack, i.e., the thickness of a contact arm body 160, a contact arm tab 110, and another contact arm body 160, is less than the thickness of the isolation member body 100. In this configuration, as the isolation member body 100 and the contact arm body 160 move laterally on the axle assembly 62, the isolation member body 100 contacts, but does not engage, any of the carriage assembly side walls 70, 74. Therefore, the contact arm bodies 160 cannot contact any of the carriage assembly side walls 70, 74 and create friction.

In an illustrative embodiment, the rear surface 104 of the isolation member body defines a generally arcuate surface 130, wherein the rear arcuate surface 130 of the isolation member body extends over a greater arc. Thus, the rear surface 104 of the isolation member body defines a generally arcuate cavity 132. The cross-sectional area of the arcuate cavity 132 corresponds to the cross-sectional area of the rotatable coupling element 57, i.e., the cross-sectional area of the bypass lug 59. In this configuration, the bypass lug 59 is structured to rotatably engage the isolation member 56.

In an illustrative embodiment, the first side surface 106 of the isolation member body is generally planar, but includes a plurality of anti-rotation lugs 140. As shown, a single non-circular anti-rotation lug 140 is provided. Each anti-rotation lug 140 is sized and shaped to correspond to an anti-rotation lug opening 86 in a side wall 70, 74 of the carriage assembly. It should be noted that in one embodiment (not shown) where there are a plurality of anti-rotation lugs 140, the anti-rotation lugs 140 and anti-rotation lug openings 86 may be generally circular.

In an illustrative embodiment, the second side surface 108 of the isolation member body is generally planar, but includes a plurality of alignment pin openings 150. The alignment pin openings 150 are sized and shaped to correspond to a plurality of alignment pins 152.

It should be noted that the embodiment of the isolation members 56 described above is for an embodiment having two isolation members 56. In this configuration, the first side surface 106 of the isolation member body is the surface that is disposed adjacent to a side wall 70, 74 of the carriage assembly when assembled, as described below. In contrast, the second side surface 108 of the isolation member body is the surface that is disposed adjacent to other isolation members 56, when assembled. Therefore, it is understood that, in an embodiment with three or more isolation members 56, only the isolation members 56 adjacent to a side wall 70, 74 of the carriage assembly would include a first side surface 106 of the isolation member body with an anti-rotation lug 140. Any middle isolation member 56 would include a first side surface 106 with a plurality of alignment pin openings 150 similar to the second side surface 108 of the isolation member body.

In an illustrative embodiment, as shown in Figures 1, 4, and 8, each contact arm 58 is substantially similar to the other and only one will be described. Each contact arm 58 includes an elongated body 160 having a first end 162, a second end 164, a first side surface 166, and a second side surface 168. In an illustrative embodiment, the contact arm body 160 is generally shaped like a "dogleg." As used herein, a "dogleg" shape includes a first elongated portion and a second elongated portion that meet at a vertex of the longitudinal axes of the respective portions. The first end 162 of the contact arm body defines an axle opening 170, a stop 172, and a biasing assembly actuator 174. The shaft opening 170 of the first end of the contact arm body (hereinafter, “contact arm opening” 170) is generally circular and is sized and shaped to correspond to the cross-sectional area of the shaft 210, which is explained below. The contact arm opening 170 extends between the first side surface 166 of the contact arm body and the second side surface 168 of the contact arm body. In another illustrative embodiment, a contact arm opening 170 closely corresponds to the size and shape of the cross-sectional area of the shaft 210.

In an illustrative embodiment, the first end stop 172 of the contact arm body (hereinafter, “contact arm stop” 172) is a generally radial extension. That is, the contact arm stop 172 extends generally radially relative to the center of the contact arm opening 170. As described below, during a reset operation, the contact arm stop 172 contacts the radial lug 128 of the front surface of the isolation member body. In an illustrative embodiment, the biasing assembly actuator 174 of the first end of the contact arm body (hereinafter, “contact arm actuator” 174) is also a generally radial extension. The contact arm actuator 174 is structured to operatively engage a biasing assembly slider 258, described below, during an overcurrent event.

A movable contact 60 engages, directly couples, or is affixed to the second end 164 of the body of each contact arm. The movable contact moves with the contact arm 58, as described below.

In an illustrative embodiment, shown in Figures 9A, the shaft assembly 62 includes a generally cylindrical shaft 210, a plurality of middle spacers 63 (one shown), a plurality of Belleville washers 204, a plurality of guide sleeves 206, and a plurality of nuts 208. The middle spacers 63 have side surfaces 68 that are a “reduced engagement area,” a “very reduced engagement area,” or an “extremely reduced area,” as described above. In this embodiment, the shaft 210 is a unitary body without a middle flange. In addition, the shaft 210 includes a threaded first end 212, a middle portion 214, and a threaded second end 218. That is, as used herein, the “first shaft end” 212 and the “second shaft end” 218 are the threaded portions.

In another illustrative embodiment, as shown in Figures 4, 7, and 9, the shaft assembly 62 includes a first shaft portion 200, a second shaft portion 202, a plurality of Belleville washers 204, a plurality of guide sleeves 206, and a plurality of nuts 208. The first shaft portion 200 and the second shaft portion 202 mate to form a shaft 210. In this illustrative embodiment, the first shaft portion 200 includes a generally cylindrical elongated body 220 having a first end 222 and a second end 224. The first end 222 of the first shaft portion is threaded. The second end 224 of the first shaft portion defines a male coupling 226. In addition, the second end 224 of the first shaft portion includes a flange 228. The second shaft portion 202 includes a generally cylindrical elongated body 230 having a first end 232 and a second end 234. The first end 232 of the second shaft portion defines a female coupling 236. The first end 232 of the second shaft portion also includes a flange 238. The second end 234 of the second shaft portion is also threaded. When the first shaft portion 200 and the second shaft portion 202 are coupled to form the shaft 210, the shaft 210 includes a first end 212 (which is the first end 222 of the body of the first shaft portion and is threaded), a middle portion 214 (which includes the two flanges 228, 238, which lie adjacent to each other and define a single “middle flange 216”), and a second end 218 (which is the second end 234 of the second shaft portion, and is threaded. That is, as used herein, the “first shaft end” 212 and the “second shaft end” 218 are the threaded portions. The middle flange 216 has two side surfaces 215, 217 that define a “reduced engagement area” or a “very reduced engagement area,” as defined above. That is, the area of The cross section of the side surfaces 215, 217 of the middle flange is a “reduced engagement area” or a “very reduced engagement area”. In an alternative embodiment, shown in Figure 9, the shaft 210 is a unitary body having the members described in this paragraph.

In any of these embodiments, the shaft 210 includes one or more non-circular portions that are structured to be disposed in non-circular shaft openings 84 where the shaft 210 attaches to the side walls 70, 74 of the carriage assembly, as described above.

The guide sleeves 206, in an illustrative embodiment, are generally disk-shaped. The Belleville washers 204 and guide sleeves 206 are structured to correspond to the shaft ends 212, 218. The Belleville washers 204 define a “reduced engagement area” or a “very reduced engagement area,” as defined above. The nuts 208 are structured to correspond to the threaded portions of the shaft ends 212, 218. In addition, an outer surface 207 of the guide sleeves 206 is sized to correspond to the shaft openings 84 of the carriage assembly side plate.

The deflection assembly 64, as shown in Figures 1, 2, and 4, includes an upper plate 250, a back plate 251, a lower plate 252, a spring holder 254, a plurality of springs 256, and a plurality of sliders 258. The upper plates 250 and the lower plates 252 of the deflection assembly include a plurality of generally parallel guide slots 260. Each slider 258 includes a body 270 having an axial surface 272, an angled surface 274, an upper surface 276, and a lower surface 278. In addition, a guide member 280 is provided on each upper surface 276 and lower surface 278 of the slider.

The biasing assembly 64 is assembled as follows. The upper plate 250 and the lower plate 252 engage the rear plate 251 and the spring support 254 and are maintained in a spaced apart relationship. Each slider 258 is disposed between the upper plate 250 and the lower plate 252, with the guide members 280 disposed in the slots 260. In this configuration, the movement of the sliders 258 is limited to a generally straight path displacement. That is, each slider 258 is structured to move between a first forward position and a second retracted position. A spring 256 is disposed between each slider 258 and the spring support 254. The springs 256 bias each slider 258 toward the first position. It is understood that the biasing force generated by the springs 256 is controlled by the characteristics of the spring, as known in the art. That is, the springs 256 are structured to generate a selected biasing force.

In an illustrative embodiment, the movable contact assembly 50 is assembled as follows. In one embodiment, the shaft assembly 62 includes a first shaft portion 200 and a second shaft portion 202; the two shaft portions 200, 202 engage, directly couple, or are fixed together to form the shaft 210.

In this illustrative embodiment, as shown in Figures 3, 4, 8 and 9, there are four contact arms; a first contact arm 58A, a second contact arm 58B, a third contact arm 58C and a fourth contact arm 58D. Hereinafter, when used with reference to contact arms 58 and their elements, the letter “A” will identify the elements of the first contact arm 58A, the letter “B” will identify the elements of the second contact arm 58B, etc.

In one embodiment where the shaft assembly 62 includes one or more middle spacers 63, the middle spacers 63 are disposed in the middle portion 214 of the shaft. Next, the second contact arm 58B is coupled to the shaft 210 by passing the second end 218 of the shaft through the contact arm opening 170B and moving toward the middle portion 214 of the shaft. The second side surface 168B of the body of the second contact arm abuts, i.e., contacts, a middle spacer side surface 68. The third contact arm 58C is coupled to the shaft 210 by passing the second end 218 of the shaft through the contact arm opening 170C and moving toward the middle portion 214 of the shaft. The first side surface 166C of the body of the third contact arm abuts another middle spacer side surface 68.

In this illustrative embodiment there is a first isolation member 56A and a second isolation member 56B. Hereinafter, when used with reference to isolation members 56 and their elements, the letter “A” will identify the elements of the first isolation member 56A, the letter “B” will identify the elements of the second isolation member 56B. The first isolation member 56A is coupled to the shaft 210 by passing the first end 212 of the shaft through the opening 116A of the contact arm tab and moving toward the middle portion 214 of the shaft. The second side surface 114A of the contact arm tab abuts the first side surface 166B of the second contact arm body. The second isolation member 56B is coupled to the shaft 210 by passing the second end 218 of the shaft through the opening 116B of the contact arm tab and moving toward the middle portion 214 of the shaft. The first side surface 112B of the contact arm tab abuts the second side surface 168C of the third contact arm body.

Furthermore, the second side surface 108A of the first isolation member abuts the first side surface 106 of the second isolation member. The alignment pin openings 150A, 150B of the first and second isolation members are also aligned and an alignment pin 152 is disposed, i.e., spanning the alignment pin openings 150A, 150B of both the first and second isolation members.

The first contact arm 58A is coupled to the shaft 210 by passing the second end 218 of the shaft through the contact arm opening 170A and moving toward the shaft middle portion 214. The second side surface 168A of the body of the first contact arm abuts, i.e., contacts, the first side surface 112A of the tab for the first contact arm. The fourth contact arm 58D is coupled to the shaft 210 by passing the second end 218 of the shaft through the contact arm opening 170D and moving toward the shaft middle portion 214. The first side surface 166D of the body of the fourth contact arm abuts the second side surface 114B of the tab for the second contact arm.

In an illustrative embodiment, two Belleville washers 204 are disposed on the first end 212 of the shaft. Next, a guide sleeve 206 is disposed on the first end 212 of the shaft. Finally, a nut 208 is threadably engaged to the first end 212 of the shaft. Similarly, two Belleville washers 204 are disposed on the second end 218 of the shaft. Next, a guide sleeve 206 is disposed on the second end 218 of the shaft. Finally, a nut 208 is threadably engaged to the second end 218 of the shaft. Next, the two nuts 208 are tightened. This action compresses the Belleville washers 204. That is, the Belleville washers 204 on the first end 212 of the shaft engage the first side surface 166A of the first contact arm. Similarly, Belleville washers 204 at the second end of shaft 218 engage second side surface 168D of fourth contact arm. It should be noted that Belleville washers 204 apply only lateral bias to outer contact arms 58A, 58D, which in turn compress isolation members 56A, 56B and inner contact arms 58B, 58C. Furthermore, in an illustrative embodiment, each contact arm opening 170A, 170B, 170C, 170D corresponds to axis 210. Thus, contact arms 58A, 58B, 58C, 58D are structured to freely rotate about axis 210 with minimal friction. Furthermore, since the middle separator 63 can move laterally (axially) about the axis 210, the contact arms 58A, 58B, 58C, 58D and the isolation members 56A, 56B, i.e., the rotating elements 66, float completely on the axis 210.

In another illustrative embodiment, shown in Figure 9B, the shaft assembly 62 includes a middle flange 216. In this embodiment, the second contact arm 58B is coupled to the shaft 210 by passing the second end 218 of the shaft through the contact arm opening 170B and moving toward the shaft middle portion 214. The second side surface 168B of the body of the second contact arm abuts, i.e., contacts, the first side surface 215 of the shaft middle flange. The third contact arm 58C is coupled to the shaft 210 by passing the second end 218 of the shaft through the contact arm opening 170C and moving toward the shaft middle portion 214. The first side surface 166B of the body of the third contact arm abuts the second side surface 217 of the shaft middle flange.

In this illustrative embodiment there is a first isolation member 56A and a second isolation member 56B. Hereinafter, when used with reference to isolation members 56 and their elements, the letter “A” will identify the elements of the first isolation member 56A, the letter “B” will identify the elements of the second isolation member 56B. The first isolation member 56A is coupled to the shaft 210 by passing the first end 212 of the shaft through the opening 116A of the contact arm tab and moving toward the middle portion 214 of the shaft. The second side surface 114A of the contact arm tab abuts the first side surface 166B of the second contact arm body. The second isolation member 56B is coupled to the shaft 210 by passing the second end 218 of the shaft through the opening 116B of the contact arm tab and moving toward the middle portion 214 of the shaft. The first side surface 112B of the contact arm tab abuts the first side surface 168C of the third contact arm body.

Furthermore, the second side surface 108A of the first isolation member abuts the first side surface 106 of the second isolation member. The alignment pin openings 150A, 150B of the first and second isolation members are also aligned and an alignment pin 152 is disposed, i.e., spanning the alignment pin openings 150A, 150B of both the first and second isolation members.

The first contact arm 58A is coupled to the shaft 210 by passing the second end 218 of the shaft through the contact arm opening 170A and moving toward the shaft middle portion 214. The second side surface 168A of the body of the first contact arm abuts, i.e., contacts, the first side surface 112A of the tab for the first contact arm. The fourth contact arm 58D is coupled to the shaft 210 by passing the second end 218 of the shaft through the contact arm opening 170D and moving toward the shaft middle portion 214. The first side surface 166D of the body of the fourth contact arm abuts the second side surface 114B of the tab for the second contact arm.

In an illustrative embodiment, two Belleville washers 204 are disposed on the first end 212 of the shaft. Next, a guide sleeve 206 is disposed on the first end 212 of the shaft. Finally, a nut 208 is threadably engaged to the first end 212 of the shaft. Similarly, two Belleville washers 204 are disposed on the second end 218 of the shaft. Next, a guide sleeve 206 is disposed on the second end 218 of the shaft. Finally, a nut 208 is threadably engaged to the second end 218 of the shaft. Next, the two nuts 208 are tightened. This action compresses the Belleville washers 204. That is, the Belleville washers 204 on the first end 212 of the shaft engage the first side surface 166A of the first contact arm. Similarly, Belleville washers 204 at the second end of shaft 218 engage second side surface 168D of fourth contact arm. It should be noted that Belleville washers 204 apply only lateral bias to outer contact arms 58A, 58D, which in turn compress isolation members 56A, 56B and inner contact arms 58B, 58C. Furthermore, in an illustrative embodiment, each contact arm opening 170A, 170B, 170C, 170D corresponds to axis 210. Thus, contact arms 58A, 58B, 58C, 58D are structured to freely rotate about axis 210 with minimal friction. Furthermore, the middle flange 216 does not move laterally (axially) about the axis 210. Therefore, the contact arms 58A, 58B, 58C, 58D and the isolation members 56A, 56B, i.e., the rotating elements 66, partially float about the axis 210. That is, the rotating elements 66 on either side of the middle flange 216 float between the associated nut 208 and the middle flange 216.

It should further be noted that, in this configuration, each first end stop 172 of the contact arm body is disposed adjacent a front surface 102 of the isolation member body.

In one illustrative embodiment, the shaft 210, with the contact arms 58 and isolation members 56, is rotatably coupled to the carriage assembly 52. That is, the first and second ends 212, 218 of the shaft are disposed in or through the shaft openings 84. In one illustrative embodiment, the two Belleville washers 204 and the guide sleeve 206 are disposed generally within the shaft openings 84, with the inner Belleville washer 204 directly coupled to and engaging the adjacent contact arm 58. In another illustrative embodiment, not covered by the present invention, shown in Figure 9C, the nuts 208 are disposed outside the side walls 70, 74 of the carriage assembly and the Belleville washers 204 are disposed within the side walls 70, 74 of the carriage assembly. As before, the inner Belleville washer 204 directly engages and engages the adjacent contact arm 58. In another embodiment, the shaft 210 includes one or more non-circular portions and the shaft openings 84 have a corresponding non-circular shape. When the non-circular portions of the shaft 210 are disposed in the non-circular shaft openings 84, the shaft 210 is secured to the side walls 70, 74 of the carriage assembly. It is understood that the shaft 210 may also be secured to the side walls 70, 74 of the carriage assembly by other constructions. For example, the shaft 210 may be welded or stacked to the side walls 70, 74 of the carriage assembly (not shown).

In this configuration, the side walls 70, 74 of the carriage assembly are disposed in a spaced apart relationship. Additional spacers 76 engage both side walls 70, 74 of the carriage assembly. In addition, the biasing assembly 64 engages the side walls 70, 74 of the carriage assembly, with each slider 258 disposed adjacent a contact arm actuator 174. In addition, each anti-rotation lug 140A, 140B is disposed in an anti-rotation lug opening 86 in a side wall 70, 74 of the carriage assembly. In this configuration, the isolation members 56A, 56B are secured to the side walls 70, 74 of the carriage assembly. That is, the isolation members 56A, 56B are unable to rotate about the axis 210 and maintain their orientation relative to the side walls 70, 74 of the carriage assembly.

Therefore, in this configuration, the rotating elements 66 are floatably, or freely and floatably, coupled to the shaft assembly 62. In addition, the contact arm assembly 65 is floatably, or freely and floatably, coupled to the carriage assembly 52. Furthermore, in an embodiment where the shaft assembly 62 includes a middle spacer 63, the rotating elements 66 float completely on the shaft 210. In an embodiment where the shaft 210 includes a middle flange 216, the rotating elements 66 float partially on the shaft 210.

In an illustrative embodiment, there are two shunts 54; a first shunt 54A and a second shunt 54B. Each shunt lug 59A, 59B is rotatably coupled to an associated isolation member 56A, 56B. That is, each shunt lug 59A, 59B is rotatably disposed in the cavity defined by the rear surface of the isolation member body, arcuate surface 130A, 130B.

In this configuration, the movable contacts 60A, 60B, 60C, 60D are structured to “snap open” during an overcurrent event. That is, the contact arms 58A, 58B, 58C, 58D are structured to move between a “snap open” position and the second position of the movable contacts 60A, 60B, 60C, 60D described above. As shown in Figure 8, when the movable contacts 60A, 60B, 60C, 60D are in the second position, each movable contact 60A, 60B, 60C, 60D is in contact and electrical communication with a stationary contact 42. As current passes through the contact assembly 40, electromagnetic forces bias each movable contact 60A, 60B, 60C, 60D away from the associated stationary contact 42. Each movable contact 60A, 60B, 60C, 60D is held in the second position by the biasing assembly 64.

That is, each slider 258A, 258B, 258C, 258D engages an associated contact arm actuator 174A, 174B, 174C, 174D. In an illustrative embodiment, each slider axial surface 272A, 272B, 272C, 272D engages an associated contact arm actuator 174A, 174B, 174C, 174D. The deflection of the sliders 258A, 258B, 258C, 258D is sufficient to overcome the electromagnetic forces acting on each of the contact arms 58A, 58B, 58C, 58D under normal conditions. When an overcurrent condition occurs, the electromagnetic forces acting on each of the contact arms 58A, 58B, 58C, 58D increase and overcome the deflection of the sliders 258A, 258B, 258C, 258D. When this occurs, as shown in Figures 1 and 3, a contact arm actuator 174A, 174B, 174C (the fourth contact arm 58D is shown in the second position) compresses the associated spring 256 and allows the contact arm actuator 174A, 174B, 174C to move beneath the slider angle surface 274. This is the “slam-open position.”

That is, when the contents are in the “snapped open position,” the operating mechanism 24, and hence the carriage assembly 52, remain in the first position while the contacts 42, 60 are moved apart. It is further understood that any number of contact arms 58A, 58B, 58C, 58D may be snapped open independently of the other contact arms 58A, 58B, 58C, 58D. However, when one contact arm 58A, for example, is snapped open, current instantaneously begins to move through the other contact arms 58B, 58C, 58D. This increase in current through the other contact arms 58B, 58C, 58D causes those contact arms 58B, 58C, 58D to snap open a fraction of a second later. This fraction of a second difference is not relevant to this invention and the contact arms 58A, 58B, 58C, 58D effectively move to the snap-open position at the same time.

When the contact arms 58A, 58B, 58C, 58D are in the snap-open position, the sliders 258A, 258B, 258C, 258D bias against the associated contact arm actuator 174A, 174B, 174C, 174D and prevent the contact arms 58A, 58B, 58C, 58D from returning to the second position. When the operating mechanism 24 is actuated, thereby moving the carriage assembly 52 to the first position, the contact arms 58A, 58B, 58C, 58D engage a stop device (not shown in detail), such as the front portion 14 of the housing assembly. This engagement overcomes the deflection of the sliders 258A, 258B, 258C, 258D and rotates the contact arms 58A, 58B, 58C, 58D to the first position. Rotation of the contact arms 58A, 58B, 58C, 58D is stopped when the first end stop 172A, 172B, 172C, 172D of the contact arm body engages a radial lug 128 of the isolation member body.

In this configuration, no shunt 54A, 54B is operatively engaged with a contact arm 58A, 58B, 58C, 58D. That is, since each shunt 54A, 54B is coupled to an isolation member 56A, 56B, and since each isolation member 56A, 56B is secured to the carriage assembly 52, any force generated by a shunt 54A, 54B during an overcurrent condition is not transferred to the contact arms 58A, 58B, 58C, 58D. Furthermore, in this configuration, the contact arm assembly 65 is rotatably and floatingly coupled to the carriage assembly 52. That is, the carriage assembly 52 does not apply any lateral force on the contact arm assembly 65. Furthermore, the contact arms 58A, 58B, 58C, 58D only rotate against, i.e., create friction against, the contact arm tab side surfaces 112, 114, the middle flange side surfaces 215, 217, and the Belleville washers 204, all of which define a “reduced engagement area,” a “very reduced engagement area,” or an “extremely reduced area.” Therefore, the contact arms 58A, 58B, 58C, 58D generate only reduced friction, very reduced friction, or extremely reduced friction. Furthermore, in any embodiment, the friction is also “substantially equivalent friction.”

That is, in an illustrative embodiment, the “reduced engagement area,” “very reduced engagement area,” or “extremely reduced area” of the contact arm tab side surfaces 112, 114, the middle spacer side surfaces 68, or the middle flange side surfaces 215, 217 and Belleville washers 204 are generally equivalent, and the coefficient of friction between the contact arms 58A, 58B, 58C, 58D and the above elements 112, 114, 215, 217, 204 is generally equivalent. Therefore, the friction forces are generally balanced and the contact arms 58A, 58B, 58C, 58D float relative to the axle 210 and/or the carriage assembly 52. Alternatively stated, contact arms 58A, 58B, 58C, 58D are floatably coupled to shaft 210 and/or carriage assembly 52. Further alternatively stated, contact arm assembly 65 is floatably coupled to carriage assembly 52.

In an illustrative embodiment, each contact arm opening 170 corresponds to axis 210; that is, each contact arm opening 170A, 170B, 170C, 170D is slightly larger than axis 210, so there is negligible friction between contact arms 58A, 58B, 58C, 58D and axis 210. Therefore, contact arms 58A, 58B, 58C, 58D are freely floating relative to axis 210 and/or carriage assembly 52. Alternatively stated, contact arms 58A, 58B, 58C, 58D are freely and floatably coupled to axis 210 and/or carriage assembly 52. Further stated, alternatively, contact arm assembly 65 is freely and floatably coupled to carriage assembly 52. However, the openings 170A, 170B, 170C, 170D of the contact arms are not so large that there is an arc gap between the contact arms 58A, 58B, 58C, 58D and the shaft 210. As used herein, an “arc gap” is a gap that is of a sufficient size to allow an arc to be formed.

In an alternative embodiment, one or more contact arm openings 170A, 170B, 170C, 170D perfectly correspond to axis 210. Therefore, when a contact arm 58A, 58B, 58C, 58D with a perfectly corresponding contact arm opening 170 moves from the second snap-open position, axis 210 also rotates, thereby moving the other contact arms 58A, 58B, 58C, 58D to the snap-open position.

It should further be noted that in this configuration, i.e., a configuration where the contact arm assembly 65 is rotatably and floatably coupled to said carriage assembly 52, there may be more than two contact arms 58 because the loads on each arm are controlled for the reasons set forth above. Furthermore, as noted above, each shunt 54A, 54B has a reduced length and is arranged in a minimally curved configuration. A shunt 54A, 54B with a reduced length and arranged in a minimally curved configuration does not cause, or is subject to, extreme compound deflection. Therefore, the problems noted above are solved by the configuration of the movable contact assembly 50 described herein.

While specific embodiments of the disclosed concept have been described in detail, those skilled in the art will appreciate that various modifications and alternatives to these details could be developed in light of the general teachings of the disclosure. Accordingly, the particular provisions described are intended to be illustrative only and not limiting as to the scope of the appended claims.

Claims (6)

1. A movable contact assembly (50) for an electrical switching apparatus (10), said electrical switching apparatus (10) including a housing assembly (12) and a conductor assembly (20), said housing assembly (12) defining an enclosed space (18), said conductor assembly (20) being substantially disposed in said enclosed space (18) of the housing assembly, said conductor assembly (20) including a load conductor (34), said movable contact assembly (50) comprising: various derivations (54); a carriage assembly (52) including two side walls (70, 74) and a contact arm assembly (65); said side walls (70, 74) of the carriage assembly are arranged in a spaced apart relationship; said contact arm assembly (65) including a plurality of contact arms (58), a plurality of insulating members (56), a plurality of movable contacts (60) and an axle assembly (62); said axle assembly (62) including an axle (210); each contact arm (58) defining an opening (170); one of said movable contacts (60) is disposed on each of said contact arms (58), each of said contact arms (58) is rotatably coupled to said shaft (210), said shaft extending through said contact arm opening (170); each of said isolation members (56) is disposed adjacent to at least one contact arm (58); each insulation member (56) is coupled to, and brought into electrical communication with, said adjacent contact arm (58); said leads (54) are coupled to, and brought into electrical communication with, said insulating members (56); wherein no shunt (54) is operatively coupled to a contact arm (58); and wherein said isolation members (56) and said contact arms (58) are floatably coupled to said shaft (210) without any lateral compression and/or engagement by the side walls (70, 74) of the carriage assembly, so as to permit longitudinal movement on said shaft (210), and each contact arm (58) is exposed to substantially the same frictional forces. 2. The movable contact assembly (50) of claim 1, wherein said contact arms (58A, 58B, 58C, 58D) are compressed onto the shaft assembly (62) by a compression device (67). 3. The movable contact assembly (50) of claim 1, wherein each shunt (54) includes an elongated shunt body (90) having a length of 3.81 cm, and each shunt (54) is arranged in a curved configuration having a curvature of an arc with an inner radius greater than 1.016 cm. 4. The movable contact assembly (50) of claim 1, wherein: Each branch (54) includes a rotatable coupling element (57); Each isolation member (56) includes a rear surface (104), each of said rear surfaces (104) extending over a major arc, thereby defining a generally arcuate cavity (132): Each shunt rotating coupling element (57) is rotatably disposed in an arcuate cavity (132) of the associated isolation member; and wherein each shunt (54) is rotatably coupled to an associated isolation member (56). 5. The movable contact assembly (50) of claim 3, wherein each isolation member (56) is fixed to one of said side walls (70, 74) of the carriage assembly. 6. An electrical switching apparatus (10) comprising: a housing assembly (12) defining an enclosed space (18); a conductor assembly (20) including a fixed contact (42) and a movable contact assembly (50) according to any one of claims 1 to 5; said conductor assembly (20) is substantially disposed in said closed space (18) of the housing assembly; said movable contact assembly (50) includes several shunts (54), a carriage assembly (52), a contact arm assembly (65); said carriage assembly (52) includes two side walls (70, 74) and a contact arm assembly (65); said side walls (70, 74) of the carriage assembly are arranged in a spaced apart relationship; said contact arm assembly (65) includes a plurality of contact arms (58A, 58B, 58C, 58D), a plurality of insulating members (56A, 56B), a plurality of movable contacts (60) and a shaft assembly (62); said axle assembly (62) including an axle (210); each contact arm (58A, 58B, 58C, 58D) defines an opening (170A, 170B, 170C, 170D), one of said movable contacts (60) being disposed on each of said contact arms (58A, 58B, 58C, 58D); each of said contact arms (58A, 58B, 58C, 58D) is rotatably coupled to said shaft (210), said shaft extending through said contact arm opening (170A, 170B, 170C, 170D); Each of said insulation members (56A, 56B) includes two contact surfaces (102, 104); each of said isolation members (56A, 56B) is arranged immediately adjacent to and between two contact arms (58A, 58B, 58C, 58D); each contact surface (102, 104) of the isolation member is coupled to, and brought into electrical communication with, said adjacent contact arm (58A, 58B, 58C, 58D); said leads (54) are coupled to, and brought into electrical communication with, an isolation member (56A, 56B); and wherein each contact arm (58A, 58B, 58C, 58D) and each isolation member (56A, 56B) is floatably coupled to said shaft (210) without any lateral compression and/or engagement by the side walls (70, 74) of the carriage assembly, so as to allow longitudinal movement on said shaft (210), and each contact arm (58A, 58B, 58C, 58D) is exposed to the same frictional forces. The electrical switching apparatus (10) of claim 6 wherein: Each insulation member (56A, 56B) includes a body (100); each body (100) of the isolation member includes a contact arm tab (110); and Each contact arm tab (110) includes two side surfaces (112, 114); wherein an area in the range of 1% to 85%, 1% to 50%, or 1% to 15% of each side surface (112, 114) of the contact arm tab creates friction. The electrical switching apparatus (10) of claim 6 wherein: said plurality of contact arms (58) includes at least three contact arms; and wherein said at least three contact arms (58) are arranged on a single axis (210). The electrical switching apparatus (10) of claim 6 wherein: Each branch (54) includes a rotatable coupling element (57); Each isolation member (56A, 56B) includes a rear surface (104), each of said rear surfaces (104) extending over a major arc, thereby defining a generally arcuate cavity (132); Each shunt rotating coupling element (57) is rotatably disposed in an arcuate cavity (132) of the associated isolation member; and wherein each shunt (54) is rotatably coupled to an associated isolation member (56A, 56B).